Stray Charge in Quantum-dot Cellular Automata: A Validation of the Intercellular Hartree Approximation

LaRue, Matthew; Tougaw, D.; Will, Jeffrey D.

doi:10.1109/tnano.2013.2243466

Cited by 28 publications

(8 citation statements)

References 35 publications

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“…In addition to field calculations using the model of Section 2, we show simulations of field-clocked molecular QCA circuits, which importantly illustrate how the time-dependent clock drives molecular QCA calculations. The circuit simulations were calculated in MATLAB using an intercellular Hartree approximation (ICHA) [32,33]. Further theoretical details of the molecular circuit simulations are suppressed, as they are beyond the scope of this discussion.…”

Section: Resultsmentioning

confidence: 99%

Clock Topologies for Molecular Quantum-Dot Cellular Automata

Blair

Lent

2018

JLPEA

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Quantum-dot cellular automata (QCA) is a low-power, non-von-Neumann, general-purpose paradigm for classical computing using transistor-free logic. Here, classical bits are encoded on the charge configuration of individual computing primitives known as “cells.” A cell is a system of quantum dots with a few mobile charges. Device switching occurs through quantum mechanical inter-dot charge tunneling, and devices are interconnected via the electrostatic field. QCA devices are implemented using arrays of QCA cells. A molecular implementation of QCA may support THz-scale clocking or better at room temperature. Molecular QCA may be clocked using an applied electric field, known as a clocking field. A time-varying clocking field may be established using an array of conductors. The clocking field determines the flow of data and calculations. Various arrangements of clocking conductors are laid out, and the resulting electric field is simulated. It is shown that that control of molecular QCA can enable feedback loops, memories, planar circuit crossings, and versatile circuit grids that support feedback and memory, as well as data flow in any of the ordinal grid directions. Logic, interconnect and memory now become indistinguishable, and the von Neumann bottleneck is avoided.

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Section: Resultsmentioning

confidence: 99%

Clock Topologies for Molecular Quantum-Dot Cellular Automata

Blair

Lent

2018

JLPEA

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“…The bistable simulation engine of QCADesigner uses intercellular Hartree approximation (ICHA) assuming a simple two-state system to represent each QCA cell. A little compromise in accuracy as compared to full-basis computation is often compensated by the significantly better scalability [36]. ICHA is found to be valid and sufficient for verifying the functionality of large QCA circuits.…”

Section: Proposed Fault-tolerant Xor Gate Designsmentioning

confidence: 99%

On fault-tolerant design of Exclusive-OR gates in QCA

2017

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Design paradigms of logic circuits with Quantum-dot Cellular Automata (QCA) have been extensively studied in the recent past. Unfortunately, due to the lack of mature fabrication support, QCA-based circuits often suffer from various types of manufacturing defects and variations, and therefore, are unreliable and error-prone. QCA-based Exclusive-OR (XOR) gates are frequently used in the construction of several computing subsystems such as adders, linear feedback shift registers, parity generators and checkers. However, none of the existing designs for QCA XOR gates have considered the issue of ensuring fault-tolerance. Simulation results also show that these designs can hardly tolerate any fault. We investigate the applicability of various existing fault-tolerant schemes such as triple modular redundancy (TMR), NAND multiplexing, and majority multiplexing in the context of practical realization of QCA XOR gate. Our investigations reveal that these techniques incur prohibitively large area and delay and hence, they are unsuitable for practical scenarios. We propose here realistic designs of QCA XOR gates (in terms of area and delay) with significantly high fault-tolerance against all types of cell misplacement defects such as cell omission, cell displacement, cell misalignment and extra/additional cell deposition. Furthermore, the absence of any crossing in the proposed designs facilitates low-cost fabrication of such systems.

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“…Such randomly-located stray charge can affect QCA device operation in an uncontrollable and unpredictable way. [9][10][11] One solution to avoid the random placement of external counterions uses zwitterionic MV QCA molecules. 12,13 In zwitterionic molecules, the counterion is covalently built into the molecule and positive and negative charges reside at well-defined locations, while the molecule itself is charge neutral.…”

Section: Introductionmentioning

confidence: 99%

Ab initiostudies of counterion effects in molecular quantum‐dot cellular automata

Liza,

Coe,

et al. 2023

J Comput Chem

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Molecular quantum‐dot cellular automata (QCA) is a low‐power computing paradigm that may offer ultra‐high device densities and THz‐speed switching at room temperature. A single mixed‐valence (MV) molecule acts as an elementary QCA device known as a cell. Cells coupled locally via the electrostatic field form logic circuits. However, previously‐synthesized ionic MV molecular cells are affected by randomly‐located, nearby neutralizing counterions that can bias device states or change device characteristics, causing incorrect computational results. This ab initio study explores how non‐biasing counterions affect individual molecular cells. Additionally, we model two novel neutral, zwitterionic MV QCA molecules designed to avoid biasing and other undesirable counterionic effects. The location of the neutralizing counterion is controlled by integrating one counterion into each cell at a well‐defined, non‐biasing location. Each zwitterionic QCA candidate molecule presented here has a fixed, integrated counterion, which neutralizes the mobile charges used to encode the device state.

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Stray Charge in Quantum-dot Cellular Automata: A Validation of the Intercellular Hartree Approximation

Cited by 28 publications

References 35 publications

Clock Topologies for Molecular Quantum-Dot Cellular Automata

Clock Topologies for Molecular Quantum-Dot Cellular Automata

On fault-tolerant design of Exclusive-OR gates in QCA

Ab initiostudies of counterion effects in molecular quantum‐dot cellular automata

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